Method and arrangement for injecting additives

Abstract

A method and an apparatus for measured injection of additives into oil products and the like, in particular aims at the filling of fuel in tank farms for transport by tank trucks. Each batch of fuel shall have a pre-set proportion of additive. After each terminated filling and successively at a number larger than one, there is recorded a signal (S6) which represents discrepancies between actually supplied amount of additive and the amount which corresponds to the pre-set proportion. From the first signal (S6) there is calculated a further signal (S7) which represents discrepancies throughout said number of fillings and this further signal serves as a reference or correction value during the subsequent filling operation. A particular supply conduit (10) for fuel is adapted to give a through flow of fuel in order to remove remaining amounts of additive from the measuring system itself. The object is to obtain a substantially improved accuracy in injected proportion of additive in a batch of fuel being loaded or unloaded, and to avoid intermixing of different additives.

We claim: 
     
       1. Method for measured injection of additives into oil products and the like during successive and separate loading or unloading operations in tank farms, in particular for filling fuel to be transported by tank trucks, whereby the injection of additive is terminated before the discharge of the oil product stops in the current loading or unloading operation, and whereby a pre-set proportion of additive is to be injected into a desired batch of oil product in the loading or unloading operation concerned, the method comprising providing a first signal (S1) representing a measure of an increasing amount of oil product which accumulates during the current loading or unloading operation,   providing a second signal (S2) representing a measure of an increasing amount of additive which is injected in to the oil product during the current loading or unloading operation,   calculation of a third signal (S3) representing an amount of additive which should correspond to the present proportion of additive as represented by a fourth signal (S4),   comparing the third signal (S3) with the second signal (S2) so as to produce a fifth signal (S5), and   regulating (15) the injection of additive in response to the fifth signal (S5), characterized in that successively after each terminated loading or unloading operation a sixth signal (S6) is recorded in a number larger than one, said sixth signal representing possible discrepancies between an actually injected amount of additive and the amount which corresponds to the pre-set proportion of additive, that a recorded number of sixth signals (S6) is taken as a basis for calculating a seventh signal (S7) being representative of discrepancies occurring throughout said number of operations, and that the seventh signal is utilized for setting a reference or correction value for the second signal (S2) during a subsequent loading or unloading operation.   
     
     
       2. Method according to claim 1 characterized in that said recorded number of sixth signals (S6) being larger than five and preferrably a number equal to or larger than 10. 
     
     
       3. Method according to claim 1 characterized in that the seventh signal (S7) is calculated as an average value of the recorded sixth signals (S6). 
     
     
       4. Method according to any one of claims 1, characterized in that a register (32) for accumulated second signals (S2) at the start of each loading or unloading operation is counted up or down in response to said seventh signal (S7). 
     
     
       5. Apparatus for measured injection of additives to oil products and the like during successive and separate loading or unloading operations in tank farms, in particular for filling fuel to be transported by tank trucks, whereby the injection of additive is terminated before the discharge of the oil product stops in the current loading or unloading operation, and whereby a pre-set proportion of additive is to be injected into a desired batch of oil products in the loading or unloading operation concerned, the apparatus comprising means (11, 31) for providing a first signal (S1) representing a measure of an increasing amount of oil products which accumulates during the current loading or unloading operation,   means (22, 32) for providing a second signal (S2) representing a measure of an increasing amount of additive which is injected into the oil product during the current loading or unloading operation,   means (33A) for calculating a third signal (S3) representing an amount of additive which should correspond to the preset proportion of additive as represented by a fourth signal (S4),   means (33B) for comparing the third signal (S3) with the second signal (S2) so as to produce a fifth signal (S5), and   means (15) regulating the injection of additive in response to the fifth signal (S5), characterized by   means (37) for successively recording a sixth signal (S6) in a number larger than one after each terminated loading or unloading operation, said sixth signal (S6) representing possible discrepancies between actually injected amount of additive and the amount corresponding to the pre-set proportion of additive,   means (38) for calculating a seventh signal (S7) from a recorded number of sixth signals (S6), said seventh signal (S7) being representative of discrepancies occurring throughout said number of operations, and   means (32) for setting a reference or correction value for the second signal (S2) during a subsequent loading or unloading operation, on the basis of said seventh signal (S7).